1. Field of the Invention
The invention relates generally to connectors and more in particularly to innovative connections that have unique cruciform protrusions with sets of landing surfaces for joining the ends of channelled structural members.
Channelled structural members invented by Attwood in 1940 have become one of the most popular channelled structural members in the construction industry. It is used for scaffolding, space frames, stage construction, platforms, and kiosks and is available in every country of the World.
Channelled structural members comprise of a square sheet metal member of a substantially U-section and has side webs. A connecting base web is provided at the open side of the channel with inwardly extending flanges and downwardly turned portions forming longitudinal ribs. The longitudinal ribs have free edges that engage with the landing surfaces of the invention and define the open slot in the channelled structural member.
The prior art method of joining channelled structural members together is with steel plates, spring nuts and bolts; described in U.S. Pat. No. 2,345,650 to Attwood. (Oct. 12, 1940). The prior art method for joining channelled structural members with bolts and steel plates is visible and crude in appearance. It is this lack of sophistication in appearance of such prior art joining methods that has restricted the use of channelled structural members to industrial and construction sites, where appearances are of no concern.
2. Description of Related Art
The prior art method of joining channelled structural members is with exposed flat steel plates and bolts, This method of joining fittings can catch clothing or other objects that may come into contact with the raw edges of the flat plates.
Another weakness in prior art joining methods is with using flat plates and spring nuts to support heavy loads. There is a danger of the flat plates sliding off the channelled structural member, particularly if the load is relatively heavy or subjected to vibration. Supplemental fastening is required to ensure heavy vertical loads are adequately and safely secured in position.
A further disadvantage with prior art flat steel plates for joining channelled structural members is that they all are made with 14 mm diameter bolt holes; a case of one size fits all. This bolt clearance is excessive for smaller diameter bolts and may fail to provide a sufficiently rigid connection. Additional work is required for squaring joints and aligning channelled structural members.
Another disadvantage of the prior art joining designs is by the use of flat plates which creates crevices and gaps around the joining assembly. Where the prior art flat plates contact the rounded bends of the channelled structural member, gaps are formed that can harbour dirt and bacteria. The difficulty is to keep the joining area clean, especially in food processing, medical and pharmaceutical production plants. The prior art joining design restricts the use of channelled structural members in such clean environment.
Another prior art method of joining channelled structural members is by electric arc welding.